Light signal



May 1, 1928. 1,667,757

w. B. WELLS LIGHT SIGNAL I Filed Jan.25, 1925 INVENTOR! mf. n/4%.

BY@ :yz-M

Mh ATTORNEY lgatented May 1, 1928.

WESLEY B. WELLS,

SWITCH & SIGNAL COMPANY, OF SWI or rENNsYLvANIA.

. LIGHT Application led January lA vertical sectional view, illustratlng one form 'l of light signal embodying' my lnvention. Fig. 2 i's a sectional view along the line II-II of ]i`ig.,1.b4 f Similar reference characters refer to simi- Al5 lar parts in-both. views.

Referring to the drawing, the signal comprises a suitable yframe or housing B sup-v porting a light source, here shown-as an l electric lamp A having an incandescent filament 1. The signal also comprises collimating means, here illustrated as adoublet comprising two echelon lenses 2 andv 5. The ofront lens 2 is provided, on its inner face, with alternately disposed concentric grooves 3 and ridges 4, and the rear lens 5 is similarly provided, on its inner face, with alternately disposed concentric grooves 6 and ridges 7. The parts are so proportioned and disposed that light issuing from the filament l of the lamp A is refracted by the lens 5 so that light strikes lens 2 in paths which would, if extended, intersect in the focus ofl lens 2. The light is therefore projected from the signal in the direction of the solid lines 10 in a beam of parallel rays.l The lamp may be controlled in any suitable man'- ner and the [signal is so located that the beam of lightprojected from the front of the signal is directed towards the point from which the signal indication is to be'observed.

The apparatus thus far described is well known in the art and universally used in signaling systems. IUnder some conditions, however, stray' beams of "light, such, for exfrom the signal to give a false, or phantom,A

indication. For example, I will assume that sunlight falls upon the signal in the direction of thevbroken lines 1 1. With only7 the apparatus thus far described this sunlight ample, as rays from the sun, incident upon.

OF WILKINSBURG, PENNSYLVANIA, ASSIGNOB T0 THE UNION ssvALE, rENNsYLvANIA, A CORPORATION sIGNAL.

2a, 1925. serial No. 4,231.

would pass through the front lens, and a portion of such light would be reflected from the rear or smooth face of the rear lens and a portion would also be reflected from the .surface of the lamp A. This reflected light would then be projected from the signal and, under some conditions might be mistaken for the main beam of the signal.

This condition is undesirable, and to prevent such hantom indications I provide a screen, designated in general by the reference character D, made up of a plurality of concentric shields 8 in the-form of frustums of cones having a common apex at the focus of the lens 2. It is therefore plain that the shields 8 are parallel to the direction in which rays of light from 1am A travel between lenses 2 and 5. The ysiields 8 therefore absorb very little of the light from lamp A. The central shield 8 is further provided With\ two. Hat ribs 9 intersectingin a line passing through the Jfilament 1 of lamp A. Each shield has one edge inserted in a groove 6 o f lens 5 andthe other edge inserted in a groove 4 of lens 2.and are therefore held vrigidly in place. i

The ,shields 8y and the ribs 9 are made of opaque material and are preferablyI painted flat black to absorb a maximum amount of `the light incident upon them. It will be plain from the ,drawin that the screen D .has substantially no e ect upon the main signal beam issuing from the signal along lines 1Q, but that substantially all the light mcident'upon the signal from an o'utslde source, as along lines 11, strikes some por- "tion of screen D and is absorbed without being-reflected from the signal.

It follows that with my invention dan erous phantom indications due to the re ection of stray beams of light are substantially eliminated.

Although I have herein shown and described only one form of light signal embodying my invention, itis understood that various changes and modifications may be made therein within the scope of the appended claims Without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: Y A

'1. A light signal comprising a doublet A madey up of two lenses, a lightsource located at the focus of said doublet, andan opaque shield interposed between the two'lenses of said doublet and supported by said lenses and disposed parallel to rays from said.

2. A light signal comprising a' doublet made up of two echelon lenses each. having a plurality of concentric grooves on its inner said doublet, and a plurality of concentric lopaque frusto conical shlelds eachextendface, a light source located at the focus of ing from a the other lens.

3. A light signal comprising a doubletl l1li made up of two lenses,- a light sourcelocated at the focus of said doublet, and a plurality of concentric opaque shields located between said lenses and supported by said lenses, said shields 'being in the form of frustn-ums of n groove in one lens to a groove in 

